This is a plaster Birkenau Krematorium II model of one of the two largest crematoria and gas chambers in the Nazi concentrationary universe.
Krematorium II operated from March 31, 1943 to November 27, 1944. A wartime Allied aerial reconnaissance photo shows it when active. To the left are the undressing rooms with numbered pegs with hooks on the wall and prisoners told to remember them after the disinfecting shower.
“The crematorium is a big building with a wide chimney and 15 ovens. Under a garden there are two enormous cellars. One is where people undress and the other is the death chamber. People enter it naked and once about 3,000 are inside it is locked and they are gassed. After six or seven minutes of suffering they die,” Marcel Nadjari – took part in the preparation of the Sonderkommando uprising.
From the undressing room they went into the gas chamber. After evacuation from the gas chamber the bodies were taken by lift to the crematorium on the first floor. 
Then they were cremated in the ovens. Both